Infrared and Raman spectra, ab initio calculations, and conformational stability of CH3C(O)NCO and CF3C(O)NCO

The infrared and Raman spectra of acetyl isocyanate, CH 3 C(O)NCO, and the corresponding perfluoromethyl compound, CF 3 C(O)NCO, have been recorded for the gases and solids. Additionally, the Raman spectra of the liquids were recorded and qualitative depolarization values were obtained. From these data the conformational stability has been determined for both molecules for all three physical states. The experimental conformational stability and fundamental vibrational frequencies are compared with those obtained from ab initio Hartree-Fock gradient calculations employing the RHF/6-31G * basis set.